A desktop computer or a mobile device (e.g., a mobile phone, a smartphone, or a tablet PC) using a touch screen may include at least one display device.
In the case of a desktop computer, a user may divide a screen of a display device according to work environments. When a web browser is opened, a ‘page up’ button or a ‘page down’ button on a keyboard may be used to move a web page up or down. When a mouse is used instead of the keyboard, a scroll bar at a side of the web page may be selected by using a cursor of the mouse to move the web page up or down.
In comparison, a mobile device has a relatively small output screen size, and input methods thereof are limited. It may be difficult to divide a screen of the mobile device and use the mobile device.
Also, along with the size reduction of high-performance hardware, various applications may also be executed in the mobile device. Basic applications that are installed in the mobile device by a manufacturer and various applications that are developed by general users may be executed in the mobile device.
Although various applications for satisfying user demands are provided in the mobile device, since the mobile device is manufactured to a portable size, a display size and a user interface (UI) are limited. Therefore, it may be inconvenient for the user to execute a plurality of applications in the mobile device. For example, in the mobile device, an application execution screen is displayed on an entire area of a display to execute a single application. Afterward, in order to execute another application, the displayed application has to be closed first, and then the other application has to be executed. That is, execution and closing processes for each application have to be repeated in the mobile device to execute various applications.
Therefore, technology for displaying a plurality of application execution windows on a display has to be developed. Also, while displaying the plurality of application execution windows, a user interface for controlling the plurality of application execution windows as a user desires is necessary.